(1) Field of the invention
The present invention relates to a process for producing a shaped silicon carbide-based ceramic article. More particularly, the present invention relates to a process for producing a shaped silicon carbide-based ceramic article, for example, a fiber, filament, tape, film, sheet or flake, having superior chemical, physical and thermal properties, from a starting material comprising an organic silicone polymer.
(2) Description of the Related Art
Japanese Unexamined Patent Publication (Kokai) No. 58-215426 discloses a process for producing a shaped silicon carbide-based ceramic article, which process comprises forming a starting material comprising a polysilastyrene as disclosed in U.S. Pat. No. 4,324,901 into a shaped article, for example, a hollow article, film or fiber; applying an ultraviolet ray or electron beam radiation to the shaped article to cross-link and render the article infusible; and then heating (firing) the infusible article.
The above-mentioned process is disadvantageous in that, in the cross-linking step, the shaped article, for example, a fiber exhibits a large shrinkage and an undesirable fusion. Therefore, this process is not suitable for industrial use.
U.S. Pat. No. 4,743,411 discloses a process for producing a shaped silicon carbide article having a high quality at a high efficiency. This process comprises the steps of applying a heat treatment and/or an ultraviolet ray radiation to convert a polysilastyrene to a polycarbosilastyrene copolymer; shaping the copolymer into a shaped article by a melt-shaping method or a dry-shaping method; applying a heat treatment to the shaped copolymer article to make the shaped article infusible; and then heating (pyrolizing) the infusible shaped article in an inert gas atmosphere to convert the infusible copolymer to a silicon carbide-based ceramic.
The above-mentioned process is advantageous in that the shaped silicon carbide-based ceramic article, for example, a fiber or film, has an excellent quality in comparison to that of the conventional article, and can be produced at a high efficiency. Nevertheless, this process is disadvantageous in that, in the heat treatment step, the shaped article is incorporated with a large amount of oxygen, thus the physical properties of the resultant shaped silicon carbide-based ceramic article are not always satisfactory, and the heat treatment for the shaped copolymer article takes a long time.
U.S. Pat. No. 4,100,233 discloses a process, for producing a shaped silicon carbide based ceramic article, in which a polycarbosilane is used as a precursory silicone polymer. This process is also disadvantageous in that, in a step in which the shaped precursory silicone polymer article is cross-linked and made infusible, a large amount of oxygen is incorporated into the shaped silicone polymer article, and thus the physical properties of the resultant shaped silicon carbide-based ceramic article are not always satisfactory and the cross-linking step takes a long time.